1. Field of the Invention
This invention relates to methods of inhibiting growth of cyanobacteria bloom in freshwater environments by administering synthetic gramine compounds. The methods can be used to treat cyanobacteria in ponds, reservoirs, pools, tanks, lakes, and other fresh water environments.
Cyanobacteria, also known as blue green algae, can grow in freshwater environments and give the water a greenish and murky appearance. The large scale growth of cyanobacteria in freshwater is called algae bloom, which stresses freshwater environments. Algae blooms can decrease the dissolved oxygen level in the water, therefore stressing the fish and other marine organism populations. Moreover, algae blooms can produce significant amounts of natural toxins that poison the environment. Some cyanobacteria produce hepatotoxin or neurotoxin or both. These toxins irritate the skin and can lead to gastrointestinal inflammation if ingested. In many case, uncontrolled algae blooms kill the fish and other marine organism populations inhabiting the body of water.
There are many cyanobacteria species that will grow in freshwater and cause algae bloom. Microcystis aeruginosa is a cyanobacteria species which can form algae blooms and is the most common toxic cyanobacterial bloom in freshwater. M. aeruginosa can produce hepatotoxins and neurotoxins. Within the M. aeruginosa algae species, there are many different strains, that have been developed in isolation in different bodies of water. The different strains are quite biodiverse.
2. Description of the Related Art
Many methods have been devised to control algae growth in marine environments.
U.S. Pat. No. 4,342,547 teaches that many compounds, including a few gramine compounds, inhibit barnacle and algae attachment to watercraft surfaces. However, this patent does not teach how to inhibit toxic bloom algae growth.
U.S. Pat. No. 7,612,049 teaches that glucosamine can be used to inhibit the growth of M. aeruginosa cyanobacterium. The glucosamine should be added at a concentration of 10-50 ppm.
The 5,6-dichlorogramine compound has been shown to inhibit the growth of saltwater N. closterium algae, which is different from freshwater cyanobacteria. (Li, et al. Chinese Journal of Oceanology and Limnology, 27(2): 309-16. (2009).)
A naturally occurring gramine compound excreted from plants, N,N-dimethyl-3-amino-methylindole, has shown ability to inhibit the growth of M. aeruginosa. (Hong et al., World Academy of Science, Engineering and Technology, Vol 71: 825-29. (2010). Hong et al., World Academy of Science, Engineering and Technology, 71: 830-34. (2010).) However, according to the Hong articles, the concentration of the administered gramine compounds must be at least 8 mg/L to inhibit the growth of M. aeruginosa. 
There is a continuing need to develop methods to control toxic algae bloom while being minimally invasive to the environment. Very potent compounds that are effective at inhibiting the growth of M. aeruginosa in low concentrations while being non-toxic to the environment would be an ideal solution to the problem of toxic algae bloom.